The present invention relates generally to electrostatic paint spraying techniques, and more particularly to a test fixture used to provide a gauge to measure the amount of electrostatic wrap potential of a coating.
The automotive industry, as well as other industries, are increasingly using plastics for reducing weight, enhancing performance, and for improving the appearance of their products. With the increased use of plastics, new paints and coatings have been required in order to provide better performance and a refined appearance to the plastic articles such as vehicle body panels. In the development and testing of these new paint products, the paints are applied to plastic test panels and are tested for various features such as weathering, flexibility, scratch resistance, vulnerability to temperature variations, etc.
Electrostatic painting techniques are used to increase the efficiency of the amount of paint that transfers to the part. The use of non-electrostatic coating techniques typically results in approximately 15 to 40 percent of the coating actually adhering to the painted article while with electrostatic painting techniques, approximately 45 to 75 percent or more of the coating typically adheres to the product. With electrostatic painting techniques, the spray direction of the coating does not need to be directly at the surface of the part in order to yield a coated surface. In other words, the electrostatic coating techniques provide a static-electric charge to the coating particles so that they are attracted toward the part even if they are not sprayed directly at the part. Different coatings have a different electrostatic wrap potential. The electrostatic wrap potential is the ability of the coating to cover a surface which is not in a direct line of spray during the painting application process. Previously, there was no method of quantifying the electrostatic wrap potential for a coating other than by actually spraying pieces of fascia or other vehicle body components. Accordingly, it is an object of the present invention to provide a method of measuring electrostatic wrap potential using standard test panels.
The present invention allows lab personnel to measure electrostatic wrap potential with standard test panels. A test fixture is provided which is capable of holding test panels in a fixed repeatable position relative to a spray gun. The test fixture holds a plastic test panel in such a position as to provide a gauge to measure the amount of electrostatic wrap potential a coating has. These and other objects of the present invention are obtained by providing an electrostatic spray fixture for test panels, including a base member having a curved surface adapted to support a test panel thereon and a ground member disposed on the curved surface. The base member includes a slot disposed at one end of the curved surface and adapted for receiving a first end of a test panel. A clamp is mounted at a second end of the curved surface and is adapted to receive a second end of a test panel. The ground member is connected to a ground wire and clamp.
The method of testing the amount of electrostatic wrap of the coating includes the steps of mounting a test panel on the curved surface of the fixture and spraying an electrostatic coating at the test panel such that the curved surface has a forward portion closest to a spraying device in a direct path of the sprayed electrostatic coating, the curved surface further including a rearward portion further from the spraying device which is not in a direct spray path of the sprayed electrostatic coating wherein an amount of coating that adheres to the test panel covering the rearward portion of the curved surface can be used to quantify the electrostatic wrap of the coating.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.